A gas turbine engine operates to produce mechanical work or thrust. For land-based gas turbine engines, a generator is typically coupled to the engine through an axial shaft, such that the mechanical work is harnessed to generate electricity. A typical gas turbine engine comprises a compressor, at least one combustor, and a turbine, with the compressor and turbine coupled together through the axial shaft. In operation, air passes through the compressor, where the pressure of the air increases and then fuel is mixed with the compressed air in the combustion section. The combustion section can comprise one or more combustion chambers. The fuel and air mixture is ignited in the combustion chamber and hot combustion gases produced pass into the turbine and drive the turbine. As the turbine rotates, the compressor turns, since they are coupled together. The turning of the shaft also drives the generator.
The turbine components, which are fabricated from a variety of high-temperature alloys, are exposed to elevated operating temperatures (often upwards of 2000° F.) and pressures for a sustained period of time. Because of the elevated temperatures, pressure, vibrations, and cycling that occurs during operation of the gas turbine engine, the turbine components are known to crack, mainly as a result of thermo-mechanical fatigue (TMF). While some crack repairs can be made utilizing processes such as welding or brazing, the turbine components also have a limited component life as determined by the original equipment manufacturer. For example, according to GER 3620, a technical publication of the General Electric Company entitled Heavy Duty Gas Turbine Operating and Maintenance Considerations, gas turbine vanes of a General Electric Frame 7FA Gas Turbine Engine, which are fabricated from FSX-414, a cobalt-based alloy, are limited to two cycles of 24,000 operating hours, or a total of 48,000 hours before being discarded. These airfoil components are deemed no longer serviceable and cannot be returned to operation. As such, operators of the gas turbine engine must purchase replacement parts, but extending the usable life of these components will provide significant cost savings.